Our nation’s War of Independence, of course, began on Lexington Green, which event will be commemorated later on this month on Patriots’ Day. Our state Constitution stood as a model for the federal document created in Philadelphia seven years later. The Springfield Armory was the first and the list goes on and on.

Now, U.S. Sen. Scott Brown, a Republican, and his Democratic challenger, Elizabeth Warren, have established a new paradigm for the nation: They agreed to eschew third-party advertisements in their closely watched campaign. And they’ve been putting their money where their mouths are.

The plan is brilliant in its simplicity: If a third-party ad is run in violation of the pact, the candidate who would benefit from the ad has to pay to charity an amount equal to half the cost of the advertisement. In other words, efforts to aid one candidate end up hitting him or her in the wallet.

Brown has now paid twice. The second occasion, late last month, was because of an ad that his campaign saw as something less than a clear-cut violation of the agreement, which the two campaigns signed back in January. But Brown agreed to pay, seeking to ensure that the integrity of the pact remained.

The agreement became necessary because of the Supreme Court’s 2010 decision in the Citizens United vs. Federal Election Commission case. That 5-4 ruling effectively opened the floodgates for all manner of advertising from corporations, unions, wealthy individuals who fund the so-called super PACs. While there was a good deal of third-party advertising early on in the Brown-Warren campaign, the January agreement brought it to an almost immediate halt.

Campaigns in states across the land should look to Massachusetts to see how it’s done.